- vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 40430] GRB 251016A: Swift/UVOT Detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42354 SUBJECT: GRB 251016A: Swift/UVOT Detection DATE: 25/10/18 12:05:09 GMT FROM: s.shilling(a)lancaster.ac.uk S.P.R. Shilling (Lancaster U.) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251016A, detected by SVOM/ECLAIRs (Basa et al., GCN Circ. 42308) and Fermi/GBM (Fermi GBM team, GCN Circ. 42309), 6.66 ks after the SVOM/ECLAIRs trigger. A source is detected in the optical by the Swift/UVOT at a position that is consistent with the likely X-ray counterpart detected by the Swift/XRT (Source 1: Evans et al., GCN Circ. 42311). Preliminary detections and upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the images are: Filter T_start(ks) T_stop(ks) Exp(s) Mag u 6.66 12.6 491.7 19.13 +/- 0.26 b 6.91 12.7 296.0 18.70 +/- 0.18 v 7.42 7.67 245.8 17.52 +/- 0.15 w1 12.1 12.4 245.8 >18.93 w2 7.17 7.42 245.8 >19.05 m2 7.68 7.85 168.3 >18.66 The magnitudes reported here are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42354. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40429] GRB 251018A: Swift/UVOT Detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42353 SUBJECT: GRB 251018A: Swift/UVOT Detection DATE: 25/10/18 11:57:31 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (MSSL-UCL) and R. Gupta (NASA GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251018A 84 s after the BAT trigger (Gupta et al., GCN Circ. 42343). A source consistent with the XRT position is detected in the initial UVOT exposures. Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 84 128 44 17.98 +/- 0.08 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.101 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42353. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40428] IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42352 SUBJECT: IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/10/18 11:11:12 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-10-18 at 05:05:42.97 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.2566 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141495_22018019.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-10-18 Time: 05:05:42.97 UT RA: 321.11 (+3.09/-2.94 deg 90% PSF containment) J2000 Dec: 41.31 (+2.46/-3.51 deg 90% PSF containment) J2000 Two gamma-ray sources listed in the Fermi 4FGL-DR4 catalog are located within the 90% uncertainty region of the event, both with no clear multi-wavelength counterpart and classification: 4FGL J2118.3+4055 and 4FGL J2120.5+433, situated 1.3 deg and 2.3 deg away from the best-fit direction of our alert, respectively. We encourage follow-up observations by both ground- and space-based instruments to help identify a possible astrophysical counterpart to the candidate neutrino. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/42352. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40427] IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42351 SUBJECT: IceCube-251018A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/10/18 11:10:28 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 25-10-18 at 05:05:42.97 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. This alert has an estimated false alarm rate of 0.2566 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141495_22018019.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 25-10-18 Time: 05:05:42.97 UT RA: 321.11 (+3.09/-2.94 deg 90% PSF containment) J2000 Dec: 41.31 (+2.46/-3.51 deg 90% PSF containment) J2000 Two gamma-ray sources listed in the Fermi 4FGL-DR4 catalog are located within the 90% uncertainty region of the event, both with no clear multi-wavelength counterpart and classification: 4FGL J2118.3+4055 and 4FGL J2120.5+433, situated 1.3 deg and 2.3 deg away from the best-fit direction of our alert, respectively. We encourage follow-up observations by both ground- and space-based instruments to help identify a possible astrophysical counterpart to the candidate neutrino. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/42351. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40426] GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42350 SUBJECT: GRB 251017A: VLT/MUSE spectroscopic redshift z = 4.327 DATE: 25/10/18 10:50:11 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> L. Izzo (INAF/OACn & DARK/NBI), A. Saccardi (CEA/Irfu), M. Garnichey (LUX-Paris Obs.), M. Ferro (INAF-OABr), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (U. Leicester), A. L. Thakur (INAF-IAPS), G. Corcoran (UCD), report on behalf of the Stargate collaboration: We observed the optical afterglow (Perez-Garcia et al., GCN 42323; Antier et al., GCN 42325; Goad et al., GCN 42326; Sasada et al., GCN 42329; Lipunov et al., GCN 42330; Fu et al., GCN 42331; Mo et al., GCN 42336; Adami et al., GCN 42339; Xin et al., GCN 42341) of GRB 251017A (Gupta et al., GCN 42322; Woolf et al., GCN 42335), using the ESO VLT UT4 (Yepun) equipped with the MUSE spectrograph. The mid time of our observation was 2025 Oct 18 01:14:28 UT (16.56 hr after the GRB trigger), and consisted of 8 exposures of 700 s each. We extracted a 1D spectrum centered on the afterglow emission, using an aperture radius of 0.6 arcsec. In the reduced spectrum, which covers the wavelength range 4750 - 9330 AA, we detect a clear continuum and a trough due to Lya absorption visible at ~6470 AA. From the identification of several absorption features as due to Si II, Si II*, O I, O I*, CII, C II*, Si IV, C IV, Fe II, Al II, we infer a common redshift of z=4.327 for the GRB. We note that our spectroscopic redshift measurement is consistent with the photometric redshift value provided by Angulo et al. (GCN 42348). We acknowledge expert support from the observing staff in Paranal, in particular Robert de Rosa, Miguel Lopez, Thallis Pessi and Julien Drevon. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/42350. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40425] GRB 251016A: VLT/FORS2 Optical Observation
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42349 SUBJECT: GRB 251016A: VLT/FORS2 Optical Observation DATE: 25/10/18 09:53:25 GMT FROM: Roberto Ricci at INAF-IRA <ricci(a)ira.inaf.it> Roberto Ricci (U Rome), Niccolo Passaleva ( U Rome) and Eleonora Troja (U Rome) report: We observed the field of the short duration GRB 251016A detected by SVOM/ECLAIRs (Basa et al., GCN 42308), FERMI-GBM (Fermi GBM team, GCN 42309), CALET-GBM (Kawakubo et al., GCN 42321), Glowbug (Woolf et al., GCN 42313) and Astro Sat CZTI (Arya et al., GCN 42327) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations started on Oct 16th, 2025 at 23:45 UT (~9 hours after the SVOM trigger) and were carried out in the I_BESS filter with an average airmass of ~1.3. The GRB lies within a very crowded region at low Galactic latitude. Several optical sources are detected within the localization of Swift/XRT Source #1 (Evans et al., GCN 42311). Objects brighter than 24 AB mag have counterparts in the GAIA DR3 catalogue (Babusiaux et al., 2023), however several fainter (>24 AB mag) sources remain unmatched. Further observations are planned to determine variability. We thank the staff at the VLT for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42349. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40424] GRB 251017A: COLIBRÍ photometric redshift
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42348 SUBJECT: GRB 251017A: COLIBRÍ photometric redshift DATE: 25/10/18 09:05:51 GMT FROM: Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe(a)gmail.com> Camila Angulo (UNAM), Ny Avo Rakotondrainibe (LAM), Alan M. Watson (UNAM), Sarah Antier (IJCLAB), Dalya Akl (NYUAD), Enrique Moreno Méndez (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: COLIBRÍ performed follow-up observations of the Swift Swift GRB 251017A (Gupta et al., GCN Circ. 42322) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-18 02:20 to 03:20 UTC (from 17.65 h to 18.65 h after the trigger) and obtained 60 minutes of exposure in the g/r/i/z/y filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. After correcting for the Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.092 mag (Schlafly & Finkbeiner 2011) and fitting a power-law model to the grizy-bands using the SMC extinction curve, we derive a photometric redshift of z = 4.34+0.15-0.42 (1-sigma c.l.). We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/42348. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40423] GRB 251017A: Swift-XRT refined Analysis
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42347 SUBJECT: GRB 251017A: Swift-XRT refined Analysis DATE: 25/10/18 08:54:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Capalbi (INAF-OAR) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 5.3 ks of XRT data for GRB 251017A, from 96 s to 39.9 ks after the trigger. The data comprise 75 s in Windowed Timing (WT) mode (the first 11 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The late-time light curve (from T0+4.7 ks) can be modelled with a power-law decay with a decay index of alpha=1.1 (+0.4, -0.3). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.67 (+/-0.15). The best-fitting absorption column is 1.4 (+/-0.5) x 10^21 cm^-2, consistent with the Galactic value of 8.9 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.09 (+0.22, -0.21) and a best-fitting absorption column of 1.9 (+0.8, -0.7) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.9 (+0.8, -0.7) x 10^21 cm^-2 Galactic foreground: 8.9 x 10^20 cm^-2 Excess significance: 2.5 sigma Photon index: 2.09 (+0.22, -0.21) If the light curve continues to decay with a power-law decay index of 1.1, the count rate at T+24 hours will be 7.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x 10^-13 (3.5 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01404904. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42347. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40422] GRB 251018A: MASTER OT detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42346 SUBJECT: GRB 251018A: MASTER OT detection DATE: 25/10/18 07:51:23 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V. Lipunov, I.Panchenko, A.Kuznetsov, G.Antipov, P.Balanutsa, E.Gorbovskoy, K.Zhirkov, N.Tiurina, A.Sankovich, Ya.Kechin, Yu. Tselik, M.Shilova, A.Chasovnikov, V.Topolev, V.Senik, D.Vlasenko, V.Shumkov, K.Vetrov, P.Rudominskaya (Lomonosov MSU, SAI, Moscow), R.Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina); D.Buckley, (SAAO, South Africa) O.Gress, N.Budnev (ISU, Irkutsk), A.Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias, Spain), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella,L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) The MASTER-OAFA robotic telescope of MASTER Global Robotic Net [1-4] started Fermi (GCN 42342) and Swift GRB 251018A (Gupta et al. GCN 42343, Trigger time 2025-10-18 03:12:02UT) 105s after notice time (141s after trigger time) at 2025-10-18 03:14:24 UT (Lipunov et al. GCN 42344, cover map and OT https://master.sai.msu.ru/site/master2/observ.php?id=3017251 There is MASTER OT J184810.01-370141.6,detected since first image (03:14:24) with m_OT=16.5 at 2025-10-18 03:16:46 (unfiltered, automatically calculated) This OT was discovered by Swift-UVOT (Gupta et al. GCN 42343) and observed by TRT (S.Y.Fu et al. GCN 42345) at the same time. Observation and reduction will be continued. [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/42346. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 40421] GRB 251018A: TRT optical afterglow detection
by GCN Circulars 18 Oct '25

18 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42345 SUBJECT: GRB 251018A: TRT optical afterglow detection DATE: 25/10/18 07:07:26 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> S.Y. Fu (HUST), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), Z.P. Zhu, L.B. He, X. Liu, J. An, S.Q. Jiang, D. Xu (NAOC) report on behalf of a large collaboration: We observed the field of GRB 251018A (Gupta et al., GCN 423243) using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 2025-10-17 03:14:29.2 UT, i. e., 147 s after the trigger, and a series frames in the Sloan r filter were obtained. An uncatalogued and varying optical transient (OT) is clearly detected at the Swift-UVOT position (Gupta et al., GCN 42343), with r = 17.96 +/-0.03 (AB) at ~ 865 s post-burst, calibrated with nearby SKYMAPPER-DR2 catalog and without the Galactic extinction correction. We thus confirm that the OT is indeed the optical afterglow of the burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/42345. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0